This invention relates generally to pumps and pumping methods for the handling of slurries. Various pumps have been used for the handling of slurries, including positive displacement pumps of the cylinder-piston type. Another type of positive displacement pump for this purpose is known as the Moyno (trademark) pump, and is shown for example in U.S. Pat. No. Re. 21,374 dated Feb. 27, 1940 and U.S. Pat. No. 2,555,136 dated Apr. 25, 1950 which are of the progressive cavity type. Another type of pump makes use of a tube or pipe made of resilient material, the ends of which form inlet and discharge openings. A driven roller is arranged to collapse the tube while being driven from the inlet toward the discharge end, thereby progressively displacing the material within the tube. For certain services, the above types of pumps have disadvantages. For example, a pump of the cylinder-piston type or collapsible tube type produce pulsations or surges in the discharge, and this may be detrimental to piping and other equipment to which the pump is connectioned. Such pulsations or surges can be minimized by the use of surge preventators, but this increases space requirements and involves additional expense. Pumps of the Moyno type are not subject to serious pulsations in the discharge, but when driven relatively high speeds they are subject to mechanical vibration.
Centrifugal pumps have been used to some extent for handling slurries. The more common pump of this type employs an impeller which acts directly upon the material to impart the necessary rotary motion. In other words, either the impeller is provided with radially extending channels through which the material flows to attain the desired rotary motion, or the impeller is provided with vanes and operates within a relatively closely fitted housing. Pumps of this type likewise have disadvantages when used for handling slurries, particularly when a plurality of stages are provided to attain a desired pumping head. They are subject to clogging under certain operating conditions, and they are subject to serious abrasion due to the direct action of the impeller upon the slurry.
Another type of centrifugal pump has been developed for use on slurries, namely one of the vortex type. With such a pump, the impeller does not act upon all of the slurry passing through the pump housing. Centrifugal force is induced within a vortex chamber which communicates with the inlet and discharge outlets of the pump, by use of an impeller which is located at one side of the chamber and which induces vortical movement by hydraulic coupling. Examples of such pumps are disclosed in U.S. Pat. No. 3,294,026, dated Dec. 27, 1966, and U.S. Pat. No. 3,759,628, dated Sept. 18, 1973. Such pumps are not of the multi-stage type, and therefore they are not capable of producing relatively high discharge heads such as is frequently desired. Furthermore the multi-staging of such pumps involves certain problems, particularly if a pump is desired having high performance with respect to developed head and pumping capacity, and if a compact overall assembly is desired which can be installed where space requirements are limited.